The volume traces the intellectual history of Patanjala Yoga philosophy from the early centuries of the Common Era through the twentieth century. It also provides a systematic discussions of the philosophy of classical Yoga. Particular attention is given to the meaning of concentration (Samadhi), engrossment (samapatti) and the extra-ordinary cognitive capacities (vibhutis, siddhis) and the role that these notions play in the Yoga philosophy, which are relevant for issues currently under discussion in contemporary western philosophy of mind. The volume compares and contrasts classical yoga philosophy with classical Samkhya and with Indian Buddhist thought. Although the primary focus of the volume is on Patanjala Yoga, the system of Hatha Yoga and other satellite systems of Yoga are discussed as well, and an attempt is made to differentiate clearly the classical system of Yoga Sastra from Hatha Yoga and the other satellite systems. Some twenty-eight Sanskrit texts of Patanjala. Yoga are summarized or noted in the volume. Twenty-six volumes of Hatha Yoga and the texts of some other satellite systems are also included. Altogether the volume contains summaries and or notations for some seventy-five Sanskrit texts.